3490 



CCELENTERA TES 



rule, but either the one or the other may, without any apparent reason, arise inde- 

 pendently. It can be shown that the direction taken by the streams depends 

 on the part to which irritation is applied. 



The higher forms of the sea-pens, or those which actually resemble feathers, 

 are not found in deep water, none being recorded to- 

 exist below six hundred fathoms. Deep-sea forms have, 

 I however, been found; these being related to Umbellula 

 \ greenlandica , which has long been well known. As early 

 I as the middle of the eighteenth century, when the pres- 

 l ence of animal life at great depths was quite unknown, 

 I two specimens were brought up from a depth of two 

 I hundred and forty fathoms, sixty miles from the coast of 

 J Greenland. The polyp stocks consisted of a long, thin 

 I stem, ending in a bundle of polyps. The larger specimen 

 | was two yards long. These two specimens, soon after 

 ] being described, were lost, but a very similar form (/. 

 I thomsoni) was obtained during the Challenger expedition; 

 i and other species have been discovered in various lati- 

 lj tudes, at great depths. Two were found between Portu- 

 1 gal and Madeira, at two thousand one hundred and 

 I twenty fathoms, while U. leptocaulis was taken in the 

 1 Indian Ocean, some two thousand five hundred fathoms 

 I below the surface. The illustration on p. 3488 shows 

 I a species ( U. encrinus) from the northern seas. 



Another family of eight-rayed corals is that of the 

 j sea fans or Gorgoniidce^ of which the beautiful, horny, 

 J tree, and bush-like growths give no idea of the living 

 I coral. In order to gain an idea of the latter, we must 

 ! picture these trees thickly covered with beautiful eight- 

 ! rayed anemones. As in the case of ordinary corals, the 

 I polyps secrete the horny branches beneath their bases, 

 j and on these they rise in gracefully branching colonies. 

 All the sea fans are attached, and branch in the most 

 various ways, some in all directions, others only in one 

 plane; in some cases simple branches run out at an 

 angle or spirally, forming fans or nets, etc. In most, 

 the axis is horny and flexible, and they might be 

 called horny corals, but single calcareous particles are 

 inclosed in the axis, and its soft covering is crowded 

 with them. The different kinds of these particles, 

 found in different species, are of great importance in 

 classification. One of the most common of the group 

 is Gorgonia vemicosa. found in the Mediterranean, illus- 



CORKSCREW SEA FAN, Streb- ... 



tocaulus pulcherrim-us. trated on P- 3489- A shark s egg is shown m the illus- 

 (Natural size.) tration attached to the coral by means of its appendages. 



